The Iranian government’s charges against Jason Rezaian, the Washington Post reporter who has been jailed since July 22, are “serious” and “relate to espionage,” the journalist’s mother told CNN’s Christiane Amanpour in an interview that aired Friday.

She said she had “no idea” what the specific charges were, which were officially filed this week.

“We have hired a lawyer who represents Ali, my son, and I. But up until the time of the actual charges, Jason was not permitted access to a lawyer.”

In an interview on the show in October, Iranian Human Rights Chief Mohammad Javad Larijani said that “during the court process, it will be definitely explained and determined whether they are serious charges or they could be dropped.”

Mary Rezaian told Amanpour that nothing has been explained to her or her family.

Failing to reach a deal on Iran’s nuclear program would create a very difficult situation for the United States, former U.S. diplomat Frank Wisner told Christiane Amanpour Thursday, but remained optimistic that the gaps could be bridged.

"Both sides are negotiating very seriously, The negotiators are extremely skillful; they've made progress on a number of vitally important points, so I’m going to keep my fingers crossed because the alternative is very difficult for all of us."

A seasoned negotiator, Wisner has been engaging with Iranians on what's called "Track Two" diplomacy in the latest attempts to broker a deal on sanctions and Iran’s nuclear capability.

Many have argued that no deal is better than anything but a very good deal; the Israeli Intelligence Minister told Amanpour that failure to reach a deal would be preferable to many alternatives.

“There is enormous value in keeping up the momentum and seeing if we can get a deal," Wisner said. "If we don't get a deal we have to be concerned about the effects.”

It all started with a harmless comedy clip on Jon Stewart’s The Daily Show, in which satirical correspondent Jason Jones met with journalist Maziar Bahari in a Tehran café.

The clip marked the beginning of a partnership that would lead to Stewart’s directing and screenwriting debut. Or maybe that just happened by chance, Stewart told CNN’s Christiane Amanpour in an interview that aired Wednesday.

"I had always wanted to be in the Directors' Guild. And so I was looking for anything. And the script had come across – it could have been a Martin Lawrence, Will Smith buddy comedy. It really didn't matter to me,” he joked.

“Rosewater” tells the story of Bahari’s months-long-imprisonment in Iran following his coverage of the 2009 presidential election. Stewart told Amanpour that he and Bahari became friends after the journalist was released.

On the heels of a damning new report from the United Nations, Iranian Human Rights Chief Mohammad Javad Larijani defended his country’s detention of Washington Post Reporter Jason Rezaian.

“Unfortunately, they have been involved in activities which our security people consider those activities definitely beyond journalism,” he told CNN’s Michael Holmes, in for Christiane Amanpour. “Their detention is according to the law with the order of the judges.”

Those close to Rezaian, who has been in detention since the end of July, say that there have been no public, specific charges filed against the journalist.

“The charges [have] been raised to them by the security officials as involving activities beyond the sphere of journalism,” Larijani said.

“Accusations – when it is considered as substantial and capable of being prosecuted by law, it becomes charges. So it was not pure accusations.”

The prosecutor considers them charges “that could be – could be – well-founded.”

Iran has “good experience” fighting terrorists, and came to the aid of Iraqis against ISIS, the speaker of the Iranian parliament told CNN’s Christiane Amanpour, saying that U.S.-led airstrikes alone would not be enough to destroy the militants.

“I think it is very unlikely to destroy guerilla fighters by just dropping bombs on their heads,” Ali Larijani said through an interpreter.

Along with the president, Hassan Rouhani, and Supreme Leader, Ali Khamanei, he is one of the most powerful people in the country.

“Us, I mean Iran, went to the side of the Iraqis very early when the crisis broke out. We don't really want to broadcast it; we don't want to go to the media and talk about what we did for the Iraqis. But in practice, we defended them.”

The head of the Iranian Revolutionary Guard’s Quds Force, Qasem Soleimani, has even been photographed on the ground in Iraq.

“Terrorists cannot be destroyed by bombing them. You cannot solve terrorism by occupation. And in order to fight them effectively, you have to choose another method. And you know that we have good experience in that, because we have actually fought against them.”

Talks with Iran over its nuclear program are “the most complex negotiation I've ever seen,” Chief U.S. Negotiator Wendy Sherman told CNN’s Christiane Amanpour in an interview that aired Friday.

“The number of elements that have to be addressed – from enrichment capacity, to facilities, to research and development, to possible military dimensions, existing U.N. Security Council sanctions – I could go and on.”

“It is very complicated, very technical, many pages of annexes ultimately in any final agreement. So this takes a lot of work.”

Iran and world powers agreed, a little over a week ago, to extend negotiations four months in the hope that a permanent deal could be struck.

Iran’s foreign minister, Javad Zarif, told Amanpour that the talks are "a historic opportunity for all of us to end a rather prolonged chapter.”

“The point is whether it is possible to make a deal,” he said. “We're not talking about a bad deal or a good deal, but a doable deal. A lasting deal.”

Sherman praised all the negotiators, including Iran – and Zarif, who leads the delegation – as having been “very serious and very focused.”

Talks between world powers and Iran over that country's nuclear program are "a historic opportunity for all of us to end a rather prolonged chapter," Iranian Foreign Minister Javad Zarif told CNN's Christiane Amanpour on Thursday in Vienna.

A Sunday deadline is looming for negotiators to reach agreement on a comprehensive solution on Iran’s nuclear program; Iran, in return, is seeking broad sanctions relief and access to international markets. It now seems likely that Sunday’s deadline will not be met and may have to be extended.

"I think we have made enough serious discussion for us to think about the feasibility of continuing these discussions," Zarif said. "I think Secretary Kerry made that recommendation. I have made the recommendation."

“The point is whether it is possible to make a deal, we're not talking about a bad deal or a good deal, but a doable deal. A lasting deal.”